Optical lens generating machine having an air rotatable spherical bearing workpiece holder

ABSTRACT

An optical lens surfacing machine for separately operating upon each refractive side of an ophthalmic lens carried by a workpiece holder. An operation tool for working upon the lens surface is constructed for total lens surface engagement. The workpiece holder is supported for relatively free pivotable movement, but is power rotated for a period of time upon activation of the machine to decrease the possibility of damaging the refractive side of the lens being operated upon. This holder provides a single machine to be used for lapping and polishing a lens in a minimum number of steps.

United States Patent 11 1 Blum [ June 17, 1975 1 1 OPTICAL LENS GENERATING MACHINE HAVING AN AIR ROTATABLE SPHERICAL BEARING WORKPIECE HOLDER [75] Inventor: Raymond T. Blum, Pittsford, N.Y.

[73] Assignee: Bausch & Lomb Incorporated,

Rochester, N.Y.

221 Filed: Jan. 7, 1974 211 Appl. No.: 431,536

[52] U.S. Cl. 51/55; 51/124 L [51] Int. Cl B24b 9/I4; B24b 7/00 [58] Field of Search 51/55, 124 L [56] References Cited UNITED STATES PATENTS 1,448,239 3/1923 Schuessler 51/55 1,525,336 2/1925 Svensson.................. 2,208,527 7/1940 Houchin 51/55 Primary Examiner-Othell M. Simpson Attorney, Agent, or Firm-Frank C. Parker; Bernard D. Bogdon', Henry C. Post, 111

[57} ABSTRACT An optical lens surfacing machine for separately operating upon each refractive side of an ophthalmic lens carried by a workpiece holder. An operation tool for working upon the lens surface is constructed for total lens surface engagement. The workpiece holder is supported for relatively free pivotable movement, but is power rotated for a period of time upon activation of the machine to decrease the possibility of damaging the refractive side of the lens being operated upon. This holder provides a single machine to be used for lapping and polishing a lens in a minimum number of steps.

5 Claims, 7 Drawing Figures PATENTEIJJUN 17 ms 3. 889 .4265

saw 1 PATENTEDJUN 17 ms SHEET SHEET PATENTEI] JUN 1 7 I975 FIG. 6

FIG. 7

I OPTICAL LENS GENERATING MACHINE HAVING AN AIR ROTATABLE SPHERICAL BEARING WORKPIECE HOLDER BACKGROUND OF THE INVENTION l. Cross-Reference to Related Application This application is an improvement of the invention described in application Ser. No. 296,486, filed Oct. 10, 1972, entitled OPTICAL LENS GENERATING MACHINE HAVING SPHERICAL BEARING WORKPIECE HOLDER, for inventors Raymond T. Blum and George J. Laughman, now U.S. Pat. No. 3,828,483.

2. Field of the Invention This invention pertains to an optical lens surfacing machine for operating upon a single surface of a lens and in particular, to an optical lens surfacing machine for performing individual lapping and polishing operations upon a single surface of a lens carried by a workpiece holder for automatically aligning the lens surface with an operational tool.

SUMMARY OF THE INVENTION An optical lens surfacing machine is provided to eliminate prism defined as nonuniform lens thickness, from an ophthalmic meniscus lens and further, in separate operations to rough lap, fine lap and polish both sides of the lens to produce a finished ophthalmic lens of high quality. The simplicity of embodiments according to the principles of this invention enables a wide range of curvatures and sizes of high quality lenses to be finished at relatively inexpensive cost. In addition, disposing the work tool head above the workpiece greatly facilitates the introduction of slurry material during the processing steps and provides for automatic cleaning of the tool face for a current and subsequent operation.

It will be appreciated from this disclosure that any one machine, according to the discussed principles can be easily adjusted to accomplish rough lapping, fine lapping and polishing of either concave or convex sides of an ophthalmic lens. However, from a practical standpoint in a production situation, it is more readily desirable to set up individual machines to accomplish each task. With individual machines, a first machine initially rough generates one side of a pressed lens molded from molten material. A second machine rough generates the opposite side and removes prism. Third and fourth machines, respectively, fine lap both sides and fifth and sixth machines each polish a respective side. Oscillation is provided during the polishing step to provide breakup to produce high quality finished lenses.

Machines according to the principles of this invention can be made quite sturdy and generally have a rotational tool supported about a yoke disposed over a centrally positioned pivotable chuck for carrying the lens material being operated upon. A pivotal axis of the yoke supporting the rotational tool can be easily adjusted to insure that the rotational axis passes through the center of curvature of the lens being formed regardless of whether it is concave or convex. In addition, a fine adjustment can be accomplished by easily raising or lowering the lens material carrying chuck to further accomplish having the axis of rotation of the tool and the optical axis intersect at the center of curvature of the lens surface defined by the spherical faced operation tool.

Even though it is desirable that the initial machine setup have the rotational axis of the operation tool intersect the vertical axis of the pivotal chuck and its support pedestal at the center of curvature of the lens surface being formed by the operation tool and for the pivotal axis of the yoke to intersect a plane defined by the rotational and before mentioned vertical axis at the center of curvature, these considerations are not particularly critical. Since the setup is not particularly critical as it is for a lens generation machine where most all operational members including the lens carrier are generally rigid and accurately positioned one to the other so as to insure that the lens being formed is manufactured to design this invention is a great advance over the prior art. With the inclusion of the pivotal chuck, as in the present invention, the critical accuracies necessary for setup of typical generation machines are not required for these improved machines. The pivotal chuck provides for total surface contact between the lens material and the operation tool without disturbing the optical axis of the meniscus lens which is first identifiable after the first rough lap operation upon a pressed lens, as hereinbefore mentioned.

Because the lens material has free rotation about the optical axis and because there is total surface contact between the lens material and the operation tool, there is a possibility of the refractive surface being marred by the action of the operation tool. That is, the operation tool may operate on one area of the refractive surface of the lens material to a greater extent than on the rest of the refractive surface should the lens material not rotate about the optical axis. A rotation of the lens material for a timed duration is added to the surfacing machine to eliminate the possibility of the lens material being marred, while allowing free rotation of the lens material upon contacting the operation tool to eliminate prism from the lens.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a schmetic illustration of a lateral view of a lens surface operation tool for operation upon, for example, a convex side of a lens material held in a ball chuck.

FIG. 2 is a schematic illustration of the front view of the lens surface operation tool and ball chuck of FIG. 1, showing the pivotal axis for operational oscillation upon the convex surface of a lens material.

FIG. 3 is a cross-sectional view of a ball-bearing chuck for supporting lens material for operation upon a convex side of the lens material.

FIG. 4 is a cross-sectional view of a ball chuck for supporting lens material for operation upon a convex side of the lens material.

FIG. 5 is a cross-sectional view of a ball chuck for supporting lens material for operation upon a concave side of the lens material.

FIG. 6 is an enlarged perspective view of a selected chuck to be rotated for a timed duration about the optical axis of the lens material.

FIG. 7 is a schematic illustration of a power supply for supplying the necessary operational force to certain elements of the surfacing machine embodying the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIGS. 1 and 2 schematically illustrate lateral and front views of an embodiment constructed according to the principles of the present invention for operation upon lens material 10 to either rough lap, fine lap, or finish polish the lens material 10 into a high quality ophthalmic lens. As hereinbefore mentioned, it is most practical in a production situation to have individual machines accomplishing each of the respective lapping and polishing operations for each side of a lens being manufactured. Accordingly in FIG. 1, the illustration is for either lapping or polishing the convex surface of the lens material 10. The operation tool 12 is rotationally driven through a power driven connecting tool axis 14 to operate upon the total surface of the convex side of the lens material 10 when lowered in the downward direction of double headed arrow 16 to engage the lens material 10, as for example by the control system illus trated in FIG. 7. It is preferred that the operation tool 12 cover at least two-thirds of the lens surface when engaged therewith. Under conditions of polishing, oscillation of the operation tool 12 about the center of curvature, identified by point X, is provided. It is generally not necessary to oscillate during lapping.

In the initial setup, a chuck 18 is caused to engage and carry the lens material 10 about the optical axis B'B' to intersect the rotational axis AA' at the center of curvature X of the lens material surface being operated upon. During a lapping operation, any of the exemplary chucks shown in FIGS. 3, 4 or may be substituted for chuck 18. During each of the first two operations upon a lens material by an embodiment of the present invention, a pressing is placed in a ball-bearing chuck as illustrated in FIG. 3 to accomplish a rough lap of each respective side. A typical pressing, may be of hardened glass material having a meniscus shape formed in a mold from molten ophthalmic glass. It will be appreciated that the schematic illustration in FIG. I typically discloses an arrangement for rough lapping, fine lapping and polishing of either the convex side or the concave side of the lens material. Under any of those operations the appropriate lens operation tool 12 is incorporated for the specified operation and most usually a chuck like the chuck of FIG. 3 is included for generating or rough lapping with the appropriate tool 12 and a chuck like the chuck of FIGS. 4 or 5 is in cluded for fine lapping and polishing with the appropriate tool 12.

The configurations of the schematic illustrations in FIGS. 1 and 2 typically identifies an operational tool 12 disposed vertically above lens material engaged in the chuck 18 with a slurry introduction tube 19 present to introduce an appropriate slurry composition of fluid material during operation. This physical relationship, where the tool is above the workpiece, is maintained for all operational steps whether a step of generating, lapping, or polishing is being performed and regardless of whether a concave or convex surface of the lens material 10 is being operated upon. Although not illustrated, it is easily appreciated that slurry materials are flowed over the respective surfaces of the lens material 10 during the operational steps. It is well recognized that slurries ofdifferent composition are used in generating, lapping, or polishing processing steps. Due to the hereinbefore described physical relationship of the op' erational tool 12 vertically disposed over the lens material 10, particles of the lens material 10 that are being removed readily flow away from the work surface, particularly when a convex surface is being operated upon.

Additionally, when a concave surface is being operated upon, the lens material 10 can be removed from the chuck 18 without being subjected to being drawn through a catch basin filling with removed material, which is most likely to mar the lens material at its finished surface during the removal of the lens. A catch basin is formed if, for example, the operational tool is disposed directly below the lens material 10, as is true in some prior art devices. In addition, under conditions where a catch basin is formed by a work tool being disposed below the lens material, the basin needs to be cleaned before a next operation if a high quality operation is being performed. Otherwise, as is obvious, the undesirable previously removed materials are introduced between the lens material and work tool in the subsequent operation.

The FIG. 2 illustration emphasizes the stability of the rotational operational tool 12 engaged in the yoke 20. The yoke 20 is pivotal about an axis C'-C' which passes through the optical axis of the lens material 10 at the center of curvature X. The yoke 20 pivots about the axis C'C' while journaling in bearing supports 22 and 24, respectively, secured to center of curvature adjusting blocks 26 and 28 which are in turn affixed to a base 30. From FIG. 2, it is best seen that the base 30 provides the reference for operation and for affixing an ad justable length chuck pedestal 32 for carrying the chuck 18 which is free to pivot and rotate.

It will easily be appreciated from the description and illustrations that the center of curvature adjusting blocks 26 and 28 may be of any height size to raise or lower the axis C'C' relative to the base 30 and the chuck pedestal 32 to establish flexibility for the machine in order to manufacture a significantly wide range of curvatures for lenses whether they be for concave or convex surfaces. The center of curvature adjusting blocks 26 and 28 are for rough adjustment, while fine adjustment is accomplished by moving the adjustable length chuck pedestal 32 as needed in either of the directions identified by double headed arrow 33.

As hereinbefore mentioned, any of the three chucks, 34, 36 and 38 of FIGS. 3, 4 and 5, respectively, may be used in accomplishing the lapping and polishing operations necessary to complete surface manufacture of an ophthalmic lens. However, it has been found that during lapping the selected chuck, as for example chuck 18 or 34, may have sufficient inertia so as not to rotate about optical axis B'-B' when operation tool 12 contacts the refractive surface of lens material 10. Should such a situation occur, operation tool 12 would operate on only a portion of the refractive surface of lens material 10, thereby marring the refractive surface and the prism of lens material 10 would not be eliminated. Accordingly, as best seen in FIGS. 1, 2, 6 and 7, an annular ring 100, having an interior and an exterior surface with air scoops 102 positioned within the exterior surface, is connected about the exterior surface of the selected chuck 104. Selected chuck 104 may be any of the aforementioned chucks, i.e., chuck 18, 34, 36 or 38. An air blast from nozzle 106 is directed toward air scoops 102 for causing chuck 104 to rotate about optical axis B'B' when valve 108 is opened. As shown in FIG. 7, valve 110 for raising and lowering operation tool 12 in the direction of double headed arrow 16 is pneumatically connected with the air supply connected to valve 108. Valves 108 and 110 are opened and closed by electrical means in a conventional manner; such that, when electrical switch 112 is closed, motor 114 (which causes operation tool 12 to rotate), valves 108 and 110 are activated from power supply 116. This will apply a rotational force to selected chuck 104, while lowering rotating operation tool 12 toward lens material 10. An electrical timer 118 for deactivating valve 108 (closing the air flow to air scoops 102 via nozzle 106) is provided within the control system for limiting the rotational force to selected chuck 104 for the duration of the time needed for operation tool 12 to be lowered for contacting lens material 10.

The chuck 34 of FIG. 3 is best used to lap and remove what is generally referred to as prism, sometimes defined as the nonuniform thickness of the lens material between the refractive surfaces. After a glass pressing 40 has had, for example, a concave surface generated upon it according to the aforementioned principles of this invention, the next operational step is to rough lap the convex side of the lens material 40. This next step and subsequent surfacing steps are all by embodiments according to the principles of the present invention. As a first measure the lens material 40 is secured within a suitable seat in a rotatable chuck head 42 of the chuck 34. From FIG. 3 it will be appreciated that the chuck head 42 is rotatable about a ball bearing assembly 46 having a plurality of typically illustrated balls 45. A race 44 of the ball bearing assembly 46 is affixed to the chuck head 42 and an opposite mating race 48 is in turn affixed to a spherical bearing 50. In addition to the rotatability of the chuck head 42, the chuck head 42 is movable relative to the chuck pedestal 32 to provide automatic alignment of the lens material 40 when engaged with the operation tool 12. Toward this end, movement of the spherical bearing 40 relative to a bearing mount 52 in any 360 direction, as partially identified by double headed arrow 54 to designate movement in the plane of the illustration, may then be provided. Materials of the spherical bearing 50 and the bearing mount 52 are such that the spherical bearing 50 is able to move in, for example, either of the directions indicated by double headed arrow 54 without a great deal of force being exerted in any non-radial direction relative to the center of the spherical bearing mount 52. Due to a satifactory level of static friction force between the spherical bearing 50 and the spherical bearing mount 52, a lapping tool as surface operation tool 12, when engaged with the lens material 10, will more fully encounter any high areas on, for example, the convex lens surface of a lens having an opposite generated concave lens surface. The contact encounter at the high areas of the lens material and the surface tool will be for fractional periods of time longer than would occur if the lens material were mounted in a chuck similar to chuck 36 which is more free to move without noticeable effect due to any static friction force component. This slightly longer duration of tool and lens material encounter is all that is needed to remove high areas on the lens and to make the refractive surfaces uniformly distant from each other across the lens and thus remove prism. The level of static friction force between the spherical bearing 50 and the spherical bearing mount 52 which is necessary to accomplish these desirable results is a function of the bearing and mount materials and other factors including work tool surface material, workpiece material and rate of engagement of the tool and workpiece. In addition to the consideration of the materials of the bearing 50 and the bearing mount 52, control can be maintained on the lubricity of the contact surface between the spherical bearing 50 and bearing mount 52 by the addition of fluids or semi-solids to preclude the lens surface from moving out of engagement with the surface of the operation tool at the initial encounter to firstly allow prism to be removed. Removal of the prism takes place rapidly and the chuck stabilizes to provide full contact between the operational tool and the lens surface to continue the lapping operation with parallelism being maintained between the respective surface areas on the lens surfaces.

The chucks 36 and 38 of FIGS. 4 and 5 for convex and concave lenses, respectively, are similarly mounted. A ball pedestal 56 has end 58 threadably engaged with the chuck pedestal 32 with an opposite ball end 60 disposed within a lubricated compatible socket in a suitable bearing material 62. Both the ball end 60 and the material 62 may be of hardened steel. A snap ring 64 insures that the ball end 60 stays within the socket when the lens material is mounted and demounted from either chuck 36 or 38. From the illustrations it will be appreciated that because the ball end 60 is relatively small, it is able to be disposed particularly close to the lens surface being operated upon. This close relationship permits the center of curvature of the lens to be quite high and helps to stabilize the lens material when it is engaged with an operation tool.

It is easily appreciated that the chuck pedestal 32 in combination with the ball pedestal 56 can readily accommodate either chucks 36 or 38. Chuck 36, as is evident from the illustration of FIG. 4, provides in a threepiece construction suitable structure for carrying a lens material, for example, lens material 40 during any operational step. The bell portion 66 of the chuck 36 is formed of any suitable readily formable material such as brass. A somewhat elastic lens seat gasket 68 sits within a recess 70 formed within the bell portion 66. The third part of the three-piece construction, bearing material 62, is as hereinbefore mentioned of any suitable material for providing readily pivotable action of the chuck 36 at the ball end 60 of the ball pedestal 56. Similarly to FIG. 4, a bell 72 of FIG. 5 has a recess 74 formed therein to carry a lens mounting pad 76 for cushioning the lens material during operation.

I claim:

1. An optical lens surfacing machine for operation upon a refractive surface of an optical lens material, comprising:

an optical lens surface operation tool for operating upon the refractive surface of the lens material; means for rotatably carrying said operation tool about an axis of rotation;

support means for carrying the lens material in relatively free rotation about an optical axis of the lens material; and

pneumatic system means for applying a rotation force to said support means for a predetermined duration.

2. The invention of claim 1, wherein said pneumatic system means includes means to supply air, an annular ring with air scoops positioned therein connected to said support means and a nozzle to direct an air blast from said air supply means toward the air scoops for applying the rotation force.

3. An optical lens surfacing machine for operation upon a refractive surface of an optical lens material, comprising:

an optical lens surface operation tool for operating upon the refractive surface of the lens material; means for rotating said operation tool about an axis of rotation;

support means for carrying the lens material in relatively free rotation about an optical axis of the lens material;

means for applying a rotation force to said lens material carrying means; and

control system means for activating said rotation force applying means in response to the activation of said means for rotating said operation tool and for deactivating the rotation force applying means after a predetermined duration of time.

4. The invention of claim 3, wherein said rotation force applying means includes means to supply air, an annular ring with air scoops positioned therein connected to said support means and a nozzle to direct an air blast from said air supply means toward the air scoops for applying the rotation force.

5. The invention of claim 4, wherein said control system means includes a valve in said air supply means to be opened in response to the activation of said means for rotating said operation tool and to be closed after a predetermined duration of time. 

1. An optical lens surfacing machine for operation upon a refractive surface of an optical lens material, comprising: an optical lens surface operation tool for operating upon the refractive surface of the lens material; means for rotatably carrying said operation tool about an axis of rotation; support means for carrying the lens material in relatively free rotation about an optical axis of the lens material; and pneumatic system means for applying a rotation force to said support means for a predetermined duration.
 2. The invention of claim 1, wherein said pneumatic system means includes means to supply air, an annular ring with air scoops positioned therein connected to said support means and a nozzle to direct an air blast from said air supply means toward the air scoops for applying the rotation force.
 3. An optical lens surfacing machine for operation upon a refractive surface of an optical lens material, comprising: an optical lens surface operation tool for operating upon the refractive surface of the lens material; means for rotating said operation tool about an axis of rotation; support means for carrying the lens material in relatively free rotation about an optical axis of the lens material; means for applying a rotation force to said lens material carrying means; and control system means for activating said rotation force applying means in response to the activation of said means for rotating said operation tool and for deactivating the rotation force applying means after a predetermined duration of time.
 4. The invention of claim 3, wherein said rotation force applying means includes means to supply air, an annular ring with air scoops positioned therein connected to said support means and a nozzle to direct an air blast from said air supply means toward the air scoops for applying the rotation force.
 5. The invention of claim 4, wherein said control system means includes a valve in said air supply means to be opened in response to the activation of said means for rotating said operation tool and to be closed after a predetermined duration of time. 